Short‐term degradation of semiarid grasslands—results from a controlled‐grazing experiment in Northern China |
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| Authors: | Martin Wiesmeier Olivia Kreyling Markus Steffens Philipp Schoenbach Hongwei Wan Martin Gierus Friedhelm Taube Angelika Kölbl Ingrid Kögel‐Knabner |
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| Institution: | 1. Lehrstuhl für Bodenkunde, Department für ?kologie und ?kosystemmanagement, Wissenschaftszentrum Weihenstephan für Ern?hrung, Landnutzung und Umwelt, Technische Universit?t München, Emil‐Ramann‐Stra?e 2, 85350 Freising‐Weihenstephan, Germany;2. Institute of Crop Science and Plant Breeding–Grass and Forage Science/Organic Agriculture, Christian‐Albrechts‐Universit?t zu Kiel, 24118 Kiel, Germany |
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| Abstract: | The assessment of grassland degradation due to overgrazing is a global challenge in semiarid environments. In particular, investigations of beginning steppe degradation after a change or intensification of the land use are needed in order to detect and adjust detrimental land‐use management rapidly and thus prevent severe damages in these sensitive ecosystems. A controlled‐grazing experiment was established in Inner Mongolia (China) in 2005 that included ungrazed (UG) and heavily grazed plots with grazing intensities of 4.5 (HG4.5) and 7.5 (HG7.5) sheep per hectare. Several soil and vegetation parameters were investigated at all sites before the start of the experiment. Topsoil samples were analyzed for soil organic C (SOC), total N (Ntot), total S (Stot), and bulk density (BD). As vegetation parameters, aboveground net primary productivity (ANPP), tiller density (TD), and leaf‐area index (LAI) were determined. After 3 y of the grazing experiment, BD increased and SOC, Ntot, Stot, ANPP, and LAI significantly decreased with increasing grazing intensity. These sensitive parameters can be regarded as early‐warning indicators for degradation of semiarid grasslands. Vegetation parameters were, however, more sensitive not only to grazing but also to temporal variation of precipitation between 2006 and 2008. Contrary, soil parameters were primarily affected by grazing and resistant against climatic variations. The assessment of starting conditions in the study area and the application of defined grazing intensities is essential for the investigation of short‐term degradation in semiarid environments. |
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| Keywords: | steppe desertification soil organic carbon (SOC) overgrazing Inner Mongolia |
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